Grid system

As part of flexbox, included support for vertical and horizontal alignment classes.

Overhauled grid mixins to merge make-col-span into make-col for a singular mixin.

Added a new sm grid tier below 768px for more granular control. We now have xs, sm, md, lg, and xl. This also means every tier has been bumped up one level (so .col-md-6 in v3 is now .col-lg-6 in v4).

Changed grid system media query breakpoints and container widths to account for new grid tier and ensure columns are evenly divisible by 12 at their max width.

Grid breakpoints and container widths are now handled via Sass maps ($grid-breakpoints and $container-max-widths) instead of a handful of separate variables. These replace the @screen-* variables entirely and allow you to fully customize the grid tiers.

Media queries have also changed. Instead of repeating our media query declarations with the same value each time, we now have @include media-breakpoint-up/down/only. Now, instead of writing @media (min-width: @screen-sm-min) { ... }, you can write @include media-breakpoint-up(sm) { ... }.

Components

Dropped panels, thumbnails, and wells for a new all-encompassing component, cards.

Dropped the Glyphicons icon font. If you need icons, some options are:

Dropped the Affix jQuery plugin. We recommend using a position: sticky polyfill instead. See the HTML5 Please entry for details and specific polyfill recommendations.

If you were using Affix to apply additional, non-position styles, the polyfills might not support your use case. One option for such uses is the third-party ScrollPos-Styler library.

Dropped the pager component as it was essentially slightly customized buttons.

Refactored nearly all components to use more un-nested classes instead of children selectors.

Misc

Non-responsive usage of Bootstrap is no longer supported.

Dropped the online Customizer in favor of more extensive setup documentation and customized builds.

By component

This list highlights key changes by component between v3.x.x and v4.0.0.

Reboot

New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with our own somewhat opinionated reset styles. Selectors appearing in this file only use elements—there are no classes here. This isolates our reset styles from our component styles for a more modular approach. Some of the most important resets this includes are the box-sizing: border-box change, moving from em to rem units on many elements, link styles, and many form element resets.

Typography

Moved all .text- utilities to the _utilities.scss file.

Dropped .page-header as, aside from the border, all its styles can be applied via utilities.

.dl-horizontal has been dropped. Instead, use .row on <dl> and use grid column classes (or mixins) on its <dt> and <dd> children.

Custom <blockquote> styling has moved to classes—.blockquote and the .blockquote-reverse modifier.

.list-inline now requires that its children list items have the new .list-inline-item class applied to them.

Images

Renamed .img-responsive to .img-fluid.

Renamed .img-rounded to .rounded

Renamed .img-circle to .rounded-circle

Tables

Nearly all instances of the > selector have been removed, meaning nested tables will now automatically inherit styles from their parents. This greatly simplifies our selectors and potential customizations.

Responsive tables no longer require a wrapping element. Instead, just put the .table-responsive right on the <table>.

Buttons

Renamed .btn-default to .btn-secondary.

Dropped the .btn-xs class entirely as .btn-sm is proportionally much smaller than v3’s.

The stateful button feature of the button.js jQuery plugin has been dropped. This includes the $().button(string) and $().button('reset') methods. We advise using a tiny bit of custom JavaScript instead, which will have the benefit of behaving exactly the way you want it to.

Note that the other features of the plugin (button checkboxes, button radios, single-toggle buttons) have been retained in v4.

Overhauled the grid mixins to merge make-col and make-col-span into a single make-col mixin, thereby ensuring mixins and predefined classes utilize the same float/flex behaviors.

Added flexbox utility classes for grid system and components.

List groups

Rewrote component with flexbox.

Replaced a.list-group-item with an explicit class, .list-group-item-action, for styling link and button versions of list group items.

Added .list-group-flush class for use with cards.

Modal

Rewrote component with flexbox.

Given move to flexbox, alignment of dismiss icons in the header is likely broken as we’re no longer using floats. Floated content comes first, but with flexbox that’s no longer the case. Update your dismiss icons to come after modal titles to fix.

The remote option (which could be used to automatically load and inject external content into a modal) and the corresponding loaded.bs.modal event were removed. We recommend instead using client-side templating or a data binding framework, or calling jQuery.load yourself.

Navs

Instead of HTML-specific selectors like .nav > li > a, we use separate classes for .navs, .nav-items, and .nav-links. This makes your HTML more flexible while bringing along increased extensibility.

Navbar

The navbar has been entirely rewritten in flexbox with improved support for alignment, responsiveness, and customization.

Responsive navbar behaviors are now applied to the .navbar class via the required.navbar-toggleable-{breakpoint} where you choose where to collapse the navbar. Previously this was a Less variable modification and required recompiling.

.navbar-default is now .navbar-light, though .navbar-inverse remains the same. One of these is required on each navbar. However, these classes no longer set background-colors; instead they essentiatlly only affect color.

Navbars now require a background declaration of some kind. Choose from our background utilities (.bg-*) or set your own with the light/inverse classes above for mad customization.

Given flexbox styles, navbars can now use flexbox utilities for easy alignment options.

.navbar-toggle is now .navbar-toggler and has different styles and inner markup (no more three <span>s).

Dropped the .navbar-form class entirely. It’s no longer necessary; instead, just use .form-inline and apply margin utilities as necessary.

Navbars no longer include margin-bottom or border-radius by default. Use utilities as necessary.

All examples featuring navbars have been updated to include new markup.

Pagination

Rewrote component with flexbox.

Explicit classes (.page-item, .page-link) are now required on the descendants of .paginations

Dropped the .pager component entirely as it was little more than customized outline buttons.

Breadcrumbs

An explicit class, .breadcrumb-item, is now required on the descendants of .breadcrumbs

Labels, badges, and tags

Renamed .label to .tag to disambiguate from the <label> element.

Dropped the .badge component as it was nearly identical to labels/tags. Use the .tag-pill modifier together with the label component instead for that rounded look.

Tags are no longer floated automatically in list groups and other components. Utility classes are now required for that.

Panels, thumbnails, and wells

Dropped entirely for the new card component.

Panels

.panel to .card, now built with flexbox.

.panel-default removed and no replacement.

.panel-group removed and no replacement. .card-group is not a replacement, it is different.

.panel-heading to .card-header

.panel-title to .card-title. Depending on the desired look, you may also want to use heading elements or classes (e.g. <h3>, .h3) or bold elements or classes (e.g. <strong>, <b>, .font-weight-bold). Note that .card-title, while similarly named, produces a different look than .panel-title.

.panel-body to .card-block

.panel-footer to .card-footer

.panel-primary to .card-primary and .card-inverse (or use .bg-primary on .card-header)

.panel-success to .card-success and .card-inverse (or use .bg-success on .card-header)

.panel-info to .card-info and .card-inverse (or use .bg-info on .card-header)

.panel-warning to .card-warning and .card-inverse (or use .bg-warning on .card-header)

.panel-danger to .card-danger and .card-inverse (or use .bg-danger on .card-header)

Tooltips

Removed support for auto placement options.

Popovers

Removed support for auto placement options.

Carousel

Overhauled the entire component to simplify design and styling. We have fewer styles for you to override, new indicators, and new icons.

All CSS has been un-nested and renamed, ensuring each class is prefixed with .carousel-.

For carousel items, .next, .prev, .left, and .right are now .carousel-item-next, .carousel-item-prev, .carousel-item-left, and .carousel-item-right.

.item is also now .carousel-item.

For prev/next controls, .carousel-control.right and .carousel-control.left are now .carousel-control-right and .carousel-control-left, meaning they no longer require a specific base class.

Documentation

Our documentation received an upgrade across the board as well. Here’s the low down:

We’re still using Jekyll, but we have custom plugins in the mix:

example.rb is a fork of the default highlight.rb plugin, allowing for easier example-code handling.

callout.rb is a similar fork of that, but designed for our special docs callouts.

All docs content has been rewritten in Markdown (instead of HTML) for easier editing.

Pages have been reorganized for simpler content and a more approachable hierarchy.

We moved from regular CSS to SCSS to take full advantage of Bootstrap’s variables, mixins, and more.

Responsive utilities

All @screen- variables have been removed in v4.0.0. Use the media-breakpoint-up(), media-breakpoint-down(), or media-breakpoint-only() Sass mixins or the $grid-breakpoints Sass map instead.

The responsive utility classes have also been overhauled.

The .hidden and .show classes have been removed because they conflicted with jQuery’s $(...).hide() and $(...).show() methods. Instead, try toggling the [hidden] attribute, use inline styles like style="display: none;" and style="display: block;", or toggle the .invisible class.

The old classes (.hidden-xs.hidden-sm.hidden-md.hidden-lg.visible-xs-block.visible-xs-inline.visible-xs-inline-block.visible-sm-block.visible-sm-inline.visible-sm-inline-block.visible-md-block.visible-md-inline.visible-md-inline-block.visible-lg-block.visible-lg-inline.visible-lg-inline-block) are gone.

They have been replaced by .hidden-xs-up.hidden-xs-down.hidden-sm-up.hidden-sm-down.hidden-md-up.hidden-md-down.hidden-lg-up.hidden-lg-down.

The .hidden-*-up classes hide the element when the viewport is at the given breakpoint or larger (e.g. .hidden-md-up hides an element on medium, large, and extra-large devices).

The .hidden-*-down classes hide the element when the viewport is at the given breakpoint or smaller (e.g. .hidden-md-down hides an element on extra-small, small, and medium devices).

Rather than using explicit .visible-* classes, you make an element visible by simply not hiding it at that screen size. You can combine one .hidden-*-up class with one .hidden-*-down class to show an element only on a given interval of screen sizes (e.g. .hidden-sm-down.hidden-xl-up shows the element only on medium and large devices).

Note that the changes to the grid breakpoints in v4 means that you’ll need to go one breakpoint larger to achieve the same results (e.g. .hidden-md is more similar to .hidden-lg-down than to .hidden-md-down). The new responsive utility classes don’t attempt to accommodate less common cases where an element’s visibility can’t be expressed as a single contiguous range of viewport sizes; you will instead need to use custom CSS in such cases.